With technological advances such as electricity and the internet, humans are increasingly living in a 24-hour society that has led to substantial changes in sleeping patterns including a 2 hour reduction in average sleep duration among US adults over the past 80 years. Preliminary studies suggest that altered sleep including reductions in amount, quality, and regularity are associated with up to a 3-fold increase in the risk of cardiovascular disease (CVD) and CVD risk factors such as obesity, diabetes, and hypertension. Thus, effects on sleep may reflect one of the mechanisms by which a 21st century lifestyle predisposes to heart disease. However, the existing literature that has addressed the role of sleep largely has been limited by the lack of objective measurements of sleep and has not included a representative sample of ethnic minorities, who are at greatest risk for poor sleep. In the proposed ancillary study to the Hispanic Community Health Study (HCHS), a large US community based cohort of four Hispanic-American groups, we aim to fill this gap by collecting objective measurements of sleep patterns in 2000 study participants who are already undergoing rigorous assessment of a broad range of CVD risk factors and outcomes. Capitalizing on the HCHS resource and expanding assessments to include objective sleep pattern measurements, will provide unique and efficient opportunities to: (1) assess the prevalence of altered sleep patterns in Hispanic-Americans and assess variability among ethnic subgroups; (2) define the importance of psychosocial factors such as socioeconomic status, factors in the home and work environment and mood as well as cultural factors specific to Hispanic-Americans such as acculturation, familism, and beliefs about sleep, in predicting abnormal sleep patterns; and (3) assess the association between poor sleep and relevant cardiovascular health outcomes including obesity, hypertension, diabetes, and heart disease in Hispanic-Americans. The proposed new data and analyses will help clarify the role of sleep disorders in the development of CVD while also providing insight into the factors most responsible for poor sleep habits in the largest minority group in the US, thus establishing a framework for the development of strategies to improve sleep as a novel treatment for CVD prevention in this at risk population.